The present invention relates generally to medical devices, such as leads and catheters. More particularly, it pertains to seals or hemostasis mechanisms for medical devices such as leads and catheters.
Leads implanted in or about the heart have been used to reverse (i.e., defibrillate or cardiovert) certain life threatening arrhythmias, or to stimulate contraction (pacing) of the heart. Electrical energy is applied to the heart via the leads to return the heart to normal rhythm. Leads have also been used to sense in the atrium or ventricle of the heart and to deliver pacing pulses to the atrium or ventricle. The same lead used to sense the condition is sometimes also used in the process of delivering a corrective pulse or signal from the pulse generator of the pacemaker.
Cardiac pacing may be performed by the transvenous method or by leads implanted directly onto the ventricular epicardium. Most commonly, permanent transvenous pacing is performed using a lead positioned within one or more chambers of the heart. A lead, sometimes referred to as a catheter, may be positioned in the right ventricle or in the right atrium through a subclavian vein, and the lead terminal pins are attached to a pacemaker, which is implanted subcutaneously. The lead may also be positioned in both chambers, depending on the lead, as when a lead passes through the atrium to the ventricle. Pacing and sensing electrodes may be positioned within the atrium or the ventricle of the heart.
Pacemaker leads represent the electrical link between the pulse generator and the heart tissue, which is to be excited. These pacemaker leads include single or multiconductor coils of insulated wire having an insulating sheath. The coils provide a cylindrical envelope, many times referred to as a lumen, which provides a space into which a stiffening stylet or guidewire can be inserted. The conductive coil is connected to an electrode in an electrode assembly at a distal end of the lead.
During use, the lead conducts critical information to and from the heart. The lead, therefore, must remain in sufficient operative condition without interference from entry of bodily fluids. A lumen used as a means for deployment must remain free of blood to remain functional. Clotting blood hampers maneuverability. In addition, blood in the lumen could cause corrosion. To prevent entry of bodily fluids into the lead, a seal can be provided at the distal end of the lead. Conventional leads do not have open ends, i.e. the lumens thereof are closed. Leads which have moving parts, such as retractable fixation parts for example, use O-ring type seals to seal the distal end of the lead from entry of bodily fluids. The O-ring seals can be difficult to manufacture due to dimensional constraints which affect the effectiveness of the seal and the ease with which parts move.
Accordingly, there is a need for a lead, which is sufficiently sealed from the environment. There is also a need for a reliable means for performing cardiac sensing and pacing of the left atrium or ventricle, with a lead which is sufficiently sealed from the environment.
In one embodiment, a body-implantable lead assembly is provided comprising a lead, one end being adapted to be connected to an electrical supply for providing or receiving electrical pulses. The lead further comprises a distal tip, which is adapted to be atraumatic. The lead also has a sheath of material inert to body materials and fluids and at least one conductor extending through the lead body. The lead has a distal electrode adapted for implantation proximate to or within the heart while connected with a system for monitoring or stimulating cardiac activity. The lead, however, is not limited to use in the coronary vascular system.
In one embodiment a distal tip electrode is provided which is adapted for implantation proximate to the heart, the electrode being connected with a system for monitoring or stimulating cardiac activity.
The lead includes a seal or hemostasis mechanism. The terms xe2x80x9csealxe2x80x9d, xe2x80x9cseal mechanismxe2x80x9d and xe2x80x9chemostasis mechanismxe2x80x9d may be used interchangeably in describing the present invention. The seal can be in the form of a polymer membrane located at the distal or proximal end of the lead.
In one embodiment, the provided medical device includes an electrode tip, supplies a stylet for placement of the lead, which is sealed from exposure to fluids. The lead avoids deterioration of its function due to entry of liquid inside the lead, owing to the provision of a highly effective seal. In addition, the seal remains functional when the lead is removed for short periods of time from an environment filled or partially filled with fluid.
The present invention provides a lead, which may be positioned in or on the left ventricle to perform cardiac pacing. In one embodiment the present invention contemplates all types of over the wire leads which have an open distal end, which may be positioned in or on the left chambers of the heart for use in sensing and pacing, and/or xe2x80x9cshockingxe2x80x9d or cardioverting. The present invention is directed to left ventricular leads providing a hemostasis mechanism or seal in the lead lumen. It has been discovered that a left ventricular lead deployed over a guide wire into the coronary venous system is easily maneuvered into a desired pacing site. It has also been discovered that when the vasculature is unusually difficult or the procedure requires more time, blood can migrate into the lead lumen and begin to coagulate. This can cause undue friction between the lead and the guide wire, interfering with the maneuverability of the lead. Accordingly, the present invention provides an over the wire left ventricular lead having a hemostasis mechanism or seal, which preempts blood from entering the lead lumen.
In another embodiment, a hemostasis mechanism for left ventricular leads is provided which comprises a polymer membrane at the proximal or distal end of the lead. The membrane may be a cusp valve made of a suitable biocompatible polymer. In another embodiment, the hemostasis mechanism may be removable and disposable. This embodiment may be removably attached to the terminal pin of the left ventricular lead. In another embodiment, a grommet attachment to the terminal pin in combination with a hemostasis valve which permits the passage of the guide wire and a port for introduction of fluid are provided. The present invention also contemplates the use of the leads and seals disclosed herein as left ventricular leads.
These and other embodiments, aspects, advantages, and features of the present invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of the invention and referenced drawings or by practice of the invention. The aspects, advantages, and features of the invention are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents.